ok guys, Thanks for your help, I managed to create the hierarchy as you said.
but I have more problems in understanding the concept.
maybe this system is not what I am looking for so help me to decide .
as I told you, I want to create review system for cars.
so vehicle type -> manufacturers - > models -> submodels is the hierarchy.
now, I want that a user will be able to add a review for a certain submodel.
lets say I have a bmw 330 .
I will go to private cars (directory) go to bmw(section) go to 3 series (category) and then I need to add new something (review or content

)
for example , my fields for this will be :
year (single list box)
engine type ( text box )
gear (single list box)
performance marks (1-5) (radio buttons

)
handling marks (1-5) (radio buttons

)
would you buy from this manufacturer again (single list box)
as a user my input will be :
year - 2001
engine type - 3000
gear - automatic
performance marks (1-5)- 5
handling marks (1-5) - 5
would you buy from this manufacturer again- yes
after a user upload a review , users can see it and can give it a grade (1-10 lets say) .
can I achieve this in the jReviews system ?
if so, can you give me some guidelines please ?